|
Kerimasi
Kerimasi Volcano, also known as Kerimasi (''Mlima Kerimasi'', in Swahili language, Swahili) at is an Extinct Volcano, extinct shield volcano located in Monduli District, Arusha, Monduli District of Arusha Region in Tanzania. The majority of the mountain lies in Engaruka, Monduli, Engaruka Ward, and a quarter of it is in the Ngorongoro Conservation Area. The volcano is located in the geographic area known as the Crater Highlands and is a shield volcano that last erupted in the Pleistocene. Geology and Mineral composition Kerimasi, an extinct nephelinite volcano in northern Tanzania's eastern rift valley, emitted carbonatite tephra during its final eruptive phase. The tephra was primarily composed of alkali carbonatite, making it the earliest well-documented example of premodern natrocarbonatite volcanism. The main carbonate mineral was nyerereite, which is also the major mineral in present natrocarbonatite lava flows from the neighboring volcano Ol Doinyo Lengai, Oldoinyo Lengai. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonatites usually occur as small volcanic plug, plugs within zoned alkalic intrusive complexes, or as dike (geology), dikes, sill (geology), sills, breccias, and vein (geology), veins. They are almost exclusively associated with continental rift-related tectonic settings. It seems that there has been a steady increase in the carbonatitic igneous activity through the Earth's history, from the Archean Eon (geology), eon to the present. Nearly all carbonatite occurrences are intrusives or subvolcanic rock, subvolcanic intrusives. This is because carbonatite lava flows, being composed largely of soluble carbonates, are easily weathered and are therefore unlikely to be preserved in the geologic record. Carbonatite erupti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ngorongoro Conservation Area
The Ngorongoro Conservation Area (, ) is a protected area and a UNESCO World Heritage Site located in Ngorongoro District, west of Arusha City in Arusha Region, within the Crater Highlands geological area of northern Tanzania. The area is named after Ngorongoro Crater, a large volcanic caldera within the area. The Ngorongoro Conservation Area Authority administers the conservation area, an arm of the Tanzanian government, and its boundaries follow the boundary of the Ngorongoro District in Arusha Region. The western portion of the park abuts the Serengeti National Park (also a UNESCO World Heritage Site), and the area comprising the two parks and Kenya's Maasai Mara game reserve is home to Great Migration, a massive annual migration of millions of wildebeest, zebras, gazelles, and other animals. The conservation area also contains Olduvai Gorge, one of the most important paleoanthropological sites in the world. The 2009 Ngorongoro Wildlife Conservation Act placed new restri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arusha Region
Arusha City is a Tanzanian city and the regional capital of the Arusha Region, with a population of 416,442 plus 323,198 in the surrounding Arusha District Council (2012 census). Located below Mount Meru (Tanzania), Mount Meru on the eastern edge of the eastern branch of the East African Rift, Great Rift Valley, Arusha City has a temperate climate. The city is close to the Serengeti National Park, the Ngorongoro Conservation Area, Lake Manyara National Park, Olduvai Gorge, Tarangire National Park, Mount Kilimanjaro, and Mount Meru (Tanzania), Mount Meru in the Arusha National Park. The city is a major international diplomatic hub. It hosts the African Court on Human and Peoples' Rights, African Court of the African Union and is the capital of the East African Community. From 1994 to 2015, the city also hosted the International Criminal Tribunal for Rwanda, but that entity has ceased operations. It is a multicultural city with a majority Tanzanian population of mixed backgroun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanoes Of Tanzania
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, deep in the Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates sli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomorph
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another. The name literally means "false form". Terminology for pseudomorphs is "''replacer'' after ''original''", as in ''brookite'' after ''rutile''. Substitution pseudomorph An infiltration pseudomorph, or substitution pseudomorph is a pseudomorph in which one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but color, hardness, and other properties change to those of the replacing mineral. An example of this process is the replacement of wood by silica (quartz or opal) to form petrified wood in which the substitution may be so perfect as to retain the original cellular structure of the wood. An example of mineral-to-mineral substitution is replacement of aragonite twin crystal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on Scratch hardness, scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable. Etymology Calcite is derived from the German ''Calcit'', a term from the 19th century that came from the Latin word for Lime (material), lime, ''calx'' (genitive calcis) with the suffix "-ite" used to name minerals. It is thus etymologically related to chalk. When applied by archaeology, archaeologists and stone trade pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ol Doinyo Lengai
Ol Doinyo Lengai (Oldoinyo Lengai), "Mountain of God" in the Maasai language, is an active volcano located in the Gregory Rift, south of Lake Natron within the Arusha Region of Tanzania, Africa. Part of the volcanic system of the East African Rift, it uniquely produces natrocarbonatite lava. The 1960 eruption of Ol Doinyo Lengai led to geological investigations that finally confirmed the view that carbonatite rock is derived from magma. Geology Ol Doinyo Lengai is unique among active volcanoes in that it produces natrocarbonatite lava, a unique occurrence of volcanic carbonatite. A few older extinct carbonatite volcanoes are located nearby, including Homa Mountain. Lava Whereas most lavas are rich in silicate minerals, the lava of Ol Doinyo Lengai is a carbonatite. It is rich in the rare sodium and potassium carbonates, nyerereite and gregoryite. Due to this unusual composition, the lava erupts at relatively low temperatures of approximately . This temperature is so low that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nyerereite
Nyerereite is a very rare sodium calcium carbonate mineral with formula Na2 Ca( C O3)2. It forms colorless, platey pseudohexagonal orthorhombic crystals that are typically twinned. It has a specific gravity of 2.54 and indices of refraction of nα=1.511, nβ=1.533 and nγ=1.535. Nyerereite is not stable in contact with the atmosphere and rapidly breaks down. Collection specimens must be kept in a sealed argon environment. It has a Hermann–Mauguin notation of mm2 and the respective space group is Cmc21. In nature Nyerereite is naturally twinned and is pseudohexagonal with triad twinning; meaning that this is a six sided crystal that apparently has a hexagonal shape but is not in the hexagonal system. Triad twinning is the intergrowth of three orthorhombic crystals that turn at their center and form hexagonally shaped crystals. Nyerereite is biaxial negative, and has a 2v of 29 degrees. It shows a center acute bisectrix and a birefringence of approximately 0.023.Mckie, D., Fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natrocarbonatite
Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the East African Rift of eastern Africa. Natrocarbonatite lavas were first documented in 1962, by J B Dawson. Composition Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate minerals, nyerereite and gregoryite. Due to this unusual composition, the lava is erupted at relatively low temperatures (approximately 500-600 °C).https://www.science.org/doi/10.1126/science.245.4914.168 This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. It is also much more fluid than silicate lavas. Impact The sodium and potassium carbonate minerals of the lavas erupted at Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid weathering, the minerals are anhydrous A substance is anhydrous if it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nephelinite
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene (augite) and calcic plagioclase. Basalt, alkali basalt, basanite, tephritic nephelinite, and nephelinite differ partly in the relative proportions of plagioclase and nepheline. Alkali basalt may contain minor nepheline and does contain nepheline in its CIPW normative mineralogy. A critical ratio in the classification of these rocks is the ratio nepheline/(nepheline plus plagioclase). Basanite has a value of this ratio between 0.1 and 0.6 and also contains more than 10% olivine. Tephritic nephelinite has a value between 0.6 and 0.9. Nephelinite has a value greater than 0.9. Le Maitre (2002) defines and discusses these and other criteria in the classification of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engaruka, Monduli
Engaruka is an administrative ward in the Monduli Monduli is one of the seven districts of the Arusha Region of Tanzania. The District covers an area of . It is bordered to the north by Longido District, to the east by Arusha Rural District, to the south by the Manyara Region and to the west b ... district of the Arusha Region of Tanzania. According to the 2002 census, the ward has a total population of 7,295. References Monduli District Wards of Arusha Region {{Arusha-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monduli District
Monduli is one of the seven districts of the Arusha Region of Tanzania. The District covers an area of . It is bordered to the north by Longido District, to the east by Arusha Rural District, to the south by the Manyara Region and to the west by Ngorongoro District and Karatu District. The town of Monduli is the administrative seat of the district. According to the 2002 Tanzania National Census, the population of the Monduli District was 185,237. By 2012, the population of the district was 158,929. History The oldest site in Monduli district is the Engaruka historical site located in northwest of the district and was originally inhabited by the Iraqw peoples before they migrated south towards Karatu. The word Monduli was originated in the ward Monduli Juu. There was a wealthy Maasai ancestor with the name of Monduli, who lived in the area during the times of German colonization. The Germans colonized the area (later Tanganyika, Rwanda and Burundi) in 1880s. They brought forc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
